1. Field of the Invention
This invention relates to electronic musical instruments, and more particularly relates to such instruments capable of simulating the sound resulting from striking a natural percussion instrument.
2. Description of the Prior Art
The general nature of the harmonic spectrum of natural percussion instruments, such as a xylophone, bars, bells or chimes, has been known for some time. After a short transient or strike time period resulting from striking a percussion instrument has passed, the instrument generally emits a sustaining tone (which gradually decays) having a fundamental pitch or frequency component, together with harmonic frequency components. However, during the strike time period immediately after the instrument is struck, complex sound waves (i.e., strike tones) having complex frequency spectra are generated. In general, these complex strike tones are nonharmonic; that is, they are not integer multiples of the fundamental frequency produced by the sustaining tone of the instrument.
The electronic musical instrument industry has long sought economical techniques for simulating the sound waves produced by natural percussion instruments, especially the complex transient strike tone produced by the striking of the instruments. However, the strike tones are so complex that no economical way of simulating them has been discovered. Complex and costly electronic devices for simulating percussive sounds have been proposed in the past. For example, in a paper entitled, "The Synthesis of Audio Spectra by Means of Frequency Modulation," published in the Journal of the Audio Engineering Society, Volume 27, Number 7, dated Sep. 7, 1973, John Chowning proposes that percussive sounds, such as bells and chimes, can be simulated by frequency modulation circuitry. However, this technique requires complicated frequency modulation equipment, including means for modulating the index of modulation. The frequency modulation equipment is required by Chowning in order to produce the nonharmonic pitches required to simulate the strike tone of a natural percussion instrument.